Eartha Steward: Cruise ships leave trail of pollution in their wake

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My family has planned a cruise vacation in February. While I'm excited to visit the Caribbean, I'm unsure about the impact on the environment. How bad is a cruise's carbon footprint?

- Emmy Silverthorne

Ahoy Emmy!

I wish I had better news but cruises are on the heavy side of the carbon emissions scale. Don't get me wrong, we all deserve vacations to exotic places during our mountain winters. When choosing your vehicle of transportation to paradise, consider your carbon footprint.

Nina Rastogi, from The Green Lantern, determined carbon emissions for a seven-day Carnival cruise from Miami, via the Cayman Islands, Honduras, Belize and Mexico, to Florida (a whopping 1,826.5 miles) is equivalent to a personal emission of 2,137 pounds of CO2 (roughly a ton). A round-trip flight on a jet from Miami to Grand Cayman would emit around 340 pounds of CO2. Big difference!

Rastogi points out that a cruise ship provides more than a seat on an airplane - there's also accommodation and entertainment (which leads to a host of additional waste and environmental impacts). Not to mention the flight or drive to the destination of the cruise. That's two strikes on your carbon footprint. Ouch!

In between ports, cruise ships serve as a floating hotel and party boat. All that partying and all-you-can-eat buffets leads to more waste. Friends of the Earth found that a 3,000-passenger cruise ship (the average) produced about 210,000 gallons of human sewage, eight tons of garbage and more than 130 gallons of toxic waste on a one-week voyage. I know we like to let loose on vacation but can't we be responsible travelers at the same time?

If you remember, only a year ago, the Costa Concordia was grounded off the island of Giglio, along the Tuscan coast. With 2,380 tons of onboard fuel reserves, the damages to the environment and the popular tourist destination could have been catastrophic. As a silver lining, the incident did bring international focus on the operations of cruise lines everywhere. Especially, their impact on our planet.

Internationally, big-ship vacations have increased in popularity with nearly 20 million passengers cruising in 2012. Even though cruises allow people to see a variety of destinations all on one trip, Responsible Vacations found cruises bring limited economic benefit to local communities and small businesses.

The Daily Green reported that a cruise ship generates more air pollution than 12,000 cars in a single day. A frightening statistic when you consider that prior to 2012's new international fuel standards, most cruise lines burned a cheap grade, "dirty" fuel. Critics argue that most cruise lines get away with doing the bare minimum, squeezing through loopholes.

There are cruise lines that have made some environmental strides like the Cunard Line, which has improved the coating on the hull to reduce air emissions. Holland America purchases electricity when stationed at port, as opposed to burning more fuel. The Norwegian Cruise Line offloads used cooking oil in Hawaii for recycling into bio-diesel. At the Port of Miami, the line has donated approximately 1,300 gallons of cooking oil to an organic farmer. The farmer has converted the oil into 870 gallons of bio-diesel to power farming equipment. Celebrity Cruises has installed solar panels to power the ship's elevators and LED lights, saving up to 50 percent on energy demands.

Then there's the whale-size impact of wastewater from the ginormous ships. There are three basic types of wastewater on cruise ships. Bilge water is oily, engine run-off and condensation that collects in the bilge of the ship and is eventually pumped out. Grey water comes from onboard showers and sinks. Last is the dreaded black water, which comes from the toilets and drains of the infirmary.

In addition to sewage, it is estimated that an average cruise ship generates 1 million gallons of gray water and 25,000 gallons of oily bilge water. Most, if not all, cruise lines now employ onboard wastewater purifying systems. However, they must use mechanical, chemical and biological measures to allow the "clean" byproduct to be discharged at sea.

If you do choose a cruise, remember it is not solely the company's responsibility to ensure sustainability. Each of us, whether at home or on vacation, has to do our part to decrease our carbon footprint.

Onboard, be sure to turn off the lights when not in your cabin; don't let your eyes become bigger than your belly while grazing through the massive buffets; and take public transit or walk when at port. Also, the elevators and mechanical doors should be for folks with limited mobility. In addition to saving energy and fuel, using your legs is a great way to avoid the 10-pound souvenir around your waistline. Anchors aweigh!

Ask Eartha Steward is written by the staff at the High Country Conservation Center, a nonprofit organization dedicated to waste reduction and resource conservation. Submit questions to Eartha at eartha@highcountryconservation.org.